NSC 222 DAC Output Stages

Several Naim dealers, including Audio venue and Doug Brady HiFi, have on their webpages for the new NSC 222 lists of features of the streamer which are worded almost identically to those on the Naim brochure for the device:

There is, however, a difference that intrigues me. The dealers’ lists include

“PCM1791A DAC (running in external filter mode) followed by discrete transistor class A op-amps and filters. Custom polystyrene ultralow dielectric absorption Post DAC filter components.”

The Naim text does not have the phrase about discrete transistor class A op-amps and filters.

My understanding is that the DAC circuitry in the NSC 222 is very similar to that in the ND5 XS 2 which, unlike the NDX 2, does not have discrete circuitry for the DAC output stages. I suspect, therefore, that the Naim document linked above (which is version 3) is correct and that the dealers are working from an earlier, perhaps incorrect, version.

Please can someone give a definitive answer (@110db, perhaps)?

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Looking at the internals of the NSC222 it looks like a discrete output stage following the DAC, along the lines of the NDX2. The ND5XS2 looks to be Op Amp based.

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To me it sounds like a new DAC-design:

The DAC chip in the NSC 222 is the PCM1791A. We use a portion of it bypassing the front end with a SHARC DSP (40 bit floating point, integer oversampling). With this, low noise fixed clocks, clean power supplies, carefully chosen supporting passives and detailed PCB design it sings.

Our DSP engineers are fanatical and will not even convert from 44.1kHz to 48kHz; only integer over-sampling allowed.

The dealers would have received information direct from Naim as part of the press release. That same information would be edited for public consumption in the form of a brochure. If it’s not in the brochure, that’s doesn’t imply it’s incorrect.

Naim use these SHARC DSPs in front of all their DACs so I’m not sure that sets the 222 apart.

Hi @Hmmm,

Here’s some insight for you…however @robert_h summed it up well.

Technical text
When development has all but finished R&D writes a technical document on each new product. The documents include an overview of the product, it’s features, technical highlights, two sets of technical specs (one simple, one more complex) and an annotated photo of the internals.

These documents are used as the technical reference for Marketing to write, distributor, dealer, reviewer and customer facing material. Each edited to suit the audience. Dealers will then take the information and edit to best suit their websites and differentiation.

I had a quick look at Doug Bradys website and it all looks very well edited. I can see some of my words from the original document and re-written to make more palatable.

NSC 222 DAC Output Stages
NSC 222 does use the PCM1791A DAC in external digital filter mode, where the SHARC DSP does many audio functions. These include integer over-sampling filtering to either 705.6kHz or 768kHz depending upon the base sampling frequency. It also buffers and re-clocks asynchronous sources (S/PDIF) to eliminated associated jitter of the digital transport (as developed for nDAC).

The analogue output from the DAC is then filtered by a discrete transistor class-A ‘bop-amp’ (like an op-amp but a Naim designed op-amp specifically or the task). The filters use polystyrene capacitors. Polystyrene doesn’t sound glamorous but is the best dielectric (insulation between the capacitor plates) for audio. Polystyrene has the lowest dielectric charge absorption compared to alternative capacitors, such as teflon, polyester, paper, polycarbonate etc. They are jigged to stand up from the PCB to minimise microphonic noise. These capacitors are custom, rare, expensive and require hand soldering but we love them.

Our polystyrene capacitors are used for all filtering duties in the 200 series, not just the DAC in 222!



That’s correct, a SHARC DSP before every DAC, since nDAC. Except mu-so where we use an XMOS processor for similar algorithms. We differentiate quality by specifying component choice, the number of PSUs and suspension systems etc. All honed in the listening room.


Thank you very much Steve for your very clear and detailed answer.

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